Many Americans are appalled by the prospect of Donald Trump winning the US presidency. Many are just as scared over what might happen if he loses.

By insisting the November 8 election is rigged, the Republican nominee has stoked fears that he’s giving his supporters free rein for some kind of morning-after backlash if he loses to Democrat Hillary Clinton.

Ominously, the billionaire businessman has also urged his people to go to polling places in minority-rich places like Philadelphia and guard against voter fraud on Election Day.

What will actually happen if Trump loses is anyone’s guess. These are uncharted waters: a US presidential candidate claiming fraud even before the country votes in a highly decentralised system in which electoral rigging is described as practically impossible.

But if there is a drum roll of anticipation to see, with Trump’s poll numbers tumbling, if Clinton becomes America’s first female president, there is another triggered by his unsubstantiated claims of electoral shenanigans.

“I think Trump is playing with fire and he has been playing with fire for many, many months,” said Matt Dallek, associate professor of political management at George Washington University.

Violence is not a forgone conclusion, he said, but in a country with more guns than people all it takes is an armed, angry lone wolf Trump supporter for tragedy to occur.

Trump’s blustery, law and order campaign has appealed heavily to frustrated middle class and less educated whites and criticised immigrants, Muslims and other minorities.

You start whining before the game’s even over? I’d advise Mr Trump to stop whining and go try to make his case to get votes

US President Barack Obama

Among other demographics, he has targeted people who feel left out by the globalised economy and embrace his vision of a once-great America now reduced to mismanaged, crime-ridden mess that cannot create or hold onto jobs, compete abroad, fight Islamist extremists or keep out undocumented migrants.

At a Trump rally Monday night in Wisconsin, 18-year old first time voter and Trump supporter Joseph Wells said he was nervous about what lies ahead if Clinton wins.

“I don’t want to call Trump supporters violent, but I mean they’ll be ticked off. They’re not going to be happy,” Wells said.

“I’ll be honest, I’m kind of scared to see how the election and the aftermath is going to unfold,” said Wells, a university student.

The latest polls show Clinton an average of seven points ahead, having pulled away from Trump as nearly a dozen women came forward to accuse him of sexual misconduct. Trump denies the allegations.

Trump is quick to resort to violent language when he talks about people who oppose or challenge him. Brawls have broken out at his rallies as Trump supporters traded blows with protesters.

But the statement that perhaps horrified people the most was his suggestion in August that gun rights activists might be able to act out somehow if Clinton wins the presidency and appoints Supreme Court justices who favour stricter gun control measures.

Referring to the constitutional clause that gives Americans the right to bear arms, Trump said: “If she gets to pick her judges, nothing you can do, folks. Although the Second Amendment people - maybe there is, I don’t know.”

A pro-Trump sheriff who has caused alarm by appearing to call for a violent uprising, doubled down on the comments when invited to speak at a Trump rally in Wisconsin Monday night.

“I’ll continue to say it. It is pitchfork and torches time in America,” boomed the Milwaukee official, David Clarke, to a roar of approval from the crowd.

The prospect of violence after the election might be mitigated if Clinton wins by a large margin and if Republicans who endorsed Trump stand up and declare the voting to have been clean, said Timothy Frye, head of the political science department at Columbia University.

“One thing that will be very important to look for is the behaviour of other politicians,” Frye said, citing Trump running mate Mike Pence, who has pledged to respect the results of the elections.

President Barack Obama on Tuesday said Trump’s claims were irresponsible and showed he lacks the thick skin needed to be president.

“You start whining before the game’s even over?” Obama said. “I’d advise Mr Trump to stop whining and go try to make his case to get votes.”

“I have never seen in my lifetime or in modern political history any presidential candidate trying to discredit the elections and the election process before votes have even taken place. It’s unprecedented,” Obama said.

“If, whenever things are going badly for you and you lose, you start blaming somebody else? Then you don’t have what it takes to be in this job.”